The logical structures of a high-speed network, called topologies, are generally divided into two classes: structured and unstructured.
Structured topologies designate topologies defined by a mathematical formalism (theoretical description). For example, the “Parallel Ports Generalized Fat Trees” (PGFT) (Zahavi E., “D-Mod-K routing providing non-blocking traffic for shift permutations on real life fat trees,” webee.technion.ac.il/publication-link/index/id/574, 2010) are described by a formula enabling the topology to be reconstructed from a set of factors. Hypercubes are also cited (Bhuyan, L. N., & Agrawal, D. P. (1984), “Generalized hypercube and hyperbus structures for a computer network,” Computers, IEEE Transactions on, 100 (4), 323-333). These network structures were theoretically designed to transmit messages efficiently between machines. To perform the transmissions efficiently within the network, routing algorithms dedicated to these topologies were developed. These algorithms are also included in the previously cited documents. Such algorithms are efficient, but usable only with the topologies according to the formalism for which they were developed.
Conversely, unstructured topologies do not follow any specific formalism and/or were not designed for routing. Generally, these are topologies not complying with a particular construction. They are potentially close to a formalism, but cannot be taken into account by the routing algorithm.
It follows that a structured topology favors the performances of routing algorithms both in terms of efficiency of routing as well as in regard to their execution time. The use of routing algorithms intended for structured topologies such as “Flattened Butterfly,” “HyperX,” “Torus” or “PGFT” confirm the benefit of this type of network topology.
However, a structured network topology is costly both in terms of network switches as well as in cables. Thus, reducing the cost of the network infrastructure by decreasing the number of network switches while preserving performance in terms of routing efficiency has become one of the concerns of network architects.
In this case, by reducing the number of network switches, the theoretical characteristics of the topology are no longer preserved and the routing algorithms specific to it are therefore no longer usable in this form. Indeed, since a step of analyzing and validating the structure of the physical topology is generally required in order to carry out a topology routing, if the structure of a topology is modified so that it is no longer suitable for the routing algorithm for which it was first intended, the routing cannot be achieved according to that routing algorithm.
In this regard, the known solutions, such as the one proposed by the “OpenSM” software for “InfiniBand,” are only concerned with physical topology. In particular, according to these solutions, if the characteristics extracted from a modified physical topology do not correspond with the expectations of the routing algorithm, a fallback solution based on an algorithm that is more generic, less efficient and more costly in terms of performance time is generally adopted.
Moreover, most current network switches use a single routing table. It is therefore not possible to consider this type of network switch like several different entities in order to mitigate a reduction in the number thereof. Furthermore, the routing table of a network communicator would be written several times with conflicting data that would not be able to be merged. Moreover, for efficient routing, a destination must be reached by two different links, independent of the link by which the packet arrives, which cannot be achieved with a single routing table per network switch.